Currently, a smart phone or a tablet PC is actively disseminated, and a technology for a contact position measurement apparatus embedded in the smart phone or the tablet PC is also actively developed. The smart phone or the tablet PC mainly includes a touch screen, and a user designates a particular coordinate of the touch screen by using a finger or a stylus pen. The user can input a particular signal in the smart phone by designating the particular coordinate of the touch screen.
The touch screen may operate based on an electricity type, an infrared light type, an ultrasonic wave type and the like, and an example of the electricity operation type may include an R type touch screen (resistive touch screen) or a C type touch screen (capacitive touch screen). Among touch screens, the R type touch screen capable of simultaneously recognizing a user's finger and a stylus pen has been widely used in the related art, but the R type touch screen has a problem in that there is a reflection due to an air space between ITO layers. More specifically, transmissivity of light penetrating a display is reduced due to the air space between the ITO layers, and an external light reflection is increased.
Accordingly, currently, the C type touch screen is widely applied. The C type touch screen operates in a mode of detecting a difference in capacitance of a transparent electrode generated by a contact of an object. However, since the touch screen has difficulty in physically distinguishing between a hand and a pen, an unintended operation error by a contact of the hand may occur when the pen is used.
The related art to solve the above mentioned problem includes a method using software for distinguishing between the hand and the pen according to a contact area, and a method including a separate position measurement apparatus such as an Electro Magnetic Resonance (EMR) technique as well as the C type touch screen. However, the method of using software cannot completely resolve the unintended operation error generated due to the contact of the hand, and the method including the separate measurement apparatus increases volume, weight, and costs by requiring additional components.
Therefore, it is required to develop a technology capable of performing a determination without the operation error when an object, such as the stylus pen, is used without using a separate position measurement apparatus.